Chapter 10 - Vitamins

Vitamins

• Essential, non‐caloric (organic) nutrients, needed in small amounts in the diet. They are vital to life and indispensable to body functions.

• They have specific roles in various biochemical reactions in the body.

Water Soluble Vitamins

• (B1) thiamin

• Folate (folic acid)

• (B2) riboflavin

• Pantothenic acid

• (B3) niacin

• Biotin

• B6 pyridoxine

• Vitamin C

• B12 cobalamin

NOT STORED

Functions of Water Soluble Vitamins

Cofactors in Enzymatic Reactions

Thiamin, Riboflavin, Niacin, Pantothenic Acid, Biotin

• Reactions related to energy metabolism

• RDA proportional to energy intake

Pyridoxine (B6)

Protein metabolism; RDA proportional to protein intake

Folate & B12

Too much folate masks vitamin B12 deficiency ‐ symptoms are pernicious anemia (megaloblastic) anemia and neurological disorder

Vitamin C

Collagen synthesis, antioxidant

Linus Pauling (1901‐1994)

• “people's needs for vitamins and other nutrients vary markedly and that to maintain good health”

• ‘Orthomolecular’

• Mental illness, cancer, CVD, common cold

• “75% of all cancer can be prevented and cured by vitamin C alone”

• RDA: 60 mg • Pauling: 12,000 mg to 40,000 mg

Vitamin C and the Common Cold

• Studies are yet to conclusively show that vitamin C can prevent or reduce the severity of colds

• Several studies found:

  • Daily dosages of vitamin C, taken regularly, do not prevent colds

• But some studies have shown:

  • Some small benefit from vitamin C in high doses (1 gram) taken at the onset of a cold

• This may shorten the duration of colds by about 1.5 days and reduce the severity of symptoms by about 40%

  • The effect may be greater in children than adults

  • In adults, doses near the UL (2 g/day) may be required to produce any effect

• The placebo effect

  • In one study, half the experimental subjects received a placebo but thought they were receiving vitamin C

  • This group reported having fewer colds than the group that had received vitamin C but thought they were receiving the placebo

Vegans and Vitamin B12

This nutrient is of concern because it’s not naturally present in plants - only in animal foods

Fat Soluble Vitamins

A,D,E and K

• Dissolve in fat

• Require bile and fat for absorption

• Stored in tissues

• May be toxic in excess

Vitamin A

“Night vision”, epithelial cell health, immune

Vitamin D

Calcium absorption and utilization - also reduces the incidence of major health problems

• everyone age 1-70 should take 600 IU vitamin a day, while those 71 and older should take 800 IU.

Sources:

• Mainly animal:

  • Liver, eggs (mainly yolk), dairy, fatty fish

• Synthesis in skin ~15 minutes in sun is good for about a weeks worth

Toxicity:

• UL = 100 µg (4,000 IU)

• Calcification of soft tissues (>Ca absorption)

• Caused by supplementation

• Never by sun!

Vitamin E

antioxidant

Vitamin K

blood clotting

Beta Carotene

Plant Vitamin A

• Red/dark orange/dark green F&V

• Precursor for Vitamin A, inefficient (1/12), but adaptable

• Low toxicity!

  • 180 mg/d β‐carotene ok

  • Turn yellow or orange after 30 mg/d…

  • Hypercarotenosis

• Excessive consumption bad for smokers!

Rickets - Children

• Vitamin D deficiency

• seizures, growth retardation, bones don’t mineralize

Osteomalacia - Adults

• Vitamin D deficiency

• bone mineralization defects

Reasons for taking supplements:

• women in their childbearing years (supplemental or enrichment sources of folic acid are recommended to reduce risk of neural tube defects in infants)

• pregnant or lactating women (they may need iron and folate)

• elderly people, who often benefit from some of the vitamins and minerals in a balanced supplement (they may choose poor diets, have trouble chewing, or absorb or metabolize less efficiently)

• strict vegetarians (they may need vitamin B12, vitamin D, iron, and zinc)

Canadian Regulations of Supplements (old)

• Vitamin and mineral supplements that are considered drugs

• Regulated in Canada by the Food and Drugs Act and Regulations Part D

  • Some vitamins at higher doses can only be sold by prescription

  • Regulations control advertising of supplements preventing recommendations of high doses

Canadian Regulations of Supplements (new)

• Non‐prescription single and multiple vitamin/mineral supplements

• Regulated in Canada by the Natural Health Products Directorate of Health Canada

  • New regulations now in effect

  • 57% of Canadians recently reported taking vitamin supplements

Natural Health Products (NHPs)

• naturally occurring substances that are used to restore or maintain good health

• often made from plants, but can also be made from animals, microorganisms and marine sources

• come in a wide variety of forms, such as tablets, capsules, tinctures, solutions, creams, ointments and drops

• can be approved for sale as long as the manufacturer can show the product has been used traditionally for at least 50 years, or if the company submits evidence from scientific studies

Canadian vs U.S. Supplement Labeling

• U.S. vitamin/mineral supplements have a Supplements Facts panel which includes the nutrient %DV

• Canadian vitamin/mineral supplements do not provide a %DV for each nutrient